Topic
Ankerite
About: Ankerite is a research topic. Over the lifetime, 859 publications have been published within this topic receiving 23960 citations.
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TL;DR: The Chikkasiddavanahalli (C.S. Halli) hill range consists of mixed sulphidic-oxide banded iron formations (BIFs) and Fe-rich phyllites (± carbonaceous), which overlie carbonated schistose and massive meta volcanics.
24 citations
01 Sep 1948
TL;DR: In this article, the following sequence of deposition was accompanied by metasomatism at each stage : Dolomite→ Anhydrite→ Halite. But no pre-anhydrite gypsum has been found; this mineral occurs as porphyroblasts and fibrous veins later than anhydrite.
Abstract: Summary The carbonate associated with the evaporites is dolomite; magnesite has not so far been found. The following sequence of deposition was accompanied by metasomatism at each stage :— Dolomite→ Anhydrite→ Halite. Evidence of replacement of dolomite by anhydrite includes irregular-sided veins, replaced fossils and pseudo-ooliths, porphyroblastic and poikiloblastic crystals. Evidence of normal primary precipitation is also presented. No pre-anhydrite gypsum has been found; this mineral occurs as porphyroblasts and fibrous veins later than anhydrite. Minor occurrences of fluorite and barite in the evaporites are noted. Carboniferous limestones in the “high” beneath Billingham have been replaced by dolomite and ankerite.
24 citations
TL;DR: Ferrocarbonatites from the lamprophyric Alpine Dyke Swarm, south Westland, New Zealand are composed of dolomite-calcite-albite-hematite and contain interstitial patches dominated by calcite as discussed by the authors.
24 citations
TL;DR: The Ljubija siderite deposits, hosted by a Carboniferous sedimentary complex within the Inner Dinarides, occur as stratabound replacement-type ore bodies in limestone blocks and as sidersite-sulfides veins in shale.
Abstract: The Ljubija siderite deposits, hosted by a Carboniferous sedimentary complex within the Inner Dinarides, occur as stratabound replacement-type ore bodies in limestone blocks and as siderite-sulfides veins in shale. Three principal types of ore textures have been recognized including massive dark siderite and ankerite, siderite with zebra texture, and siderite veins. The ore and host rocks have been investigated by a combination of inorganic (major, trace, and rare earth element concen- trations), organic (characterization of hydrocarbons includ- ing biomarkers), and stable isotope geochemical methods (isotope ratios of carbonates, sulfides, sulfates, kerogen, and individual hydrocarbons). New results indicate a marine origin of the host carbonates and a hydrothermal- metasomatic origin of the Fe mineralization. The differ- ences in ore textures (e.g., massive siderite, zebra siderite) are attributed to physicochemical variations (e.g., changes in acidity, temperature, and/or salinity) of the mineralizing fluids and to the succession and intensity of replacement of host limestone. Vein siderite was formed by precipitation from hydrothermal fluids in the late stage of mineralization. The equilibrium fractionation of stable isotopes reveals higher formation temperatures for zebra siderites (around 245°C) then for siderite vein (around 185°C). Sulfur isotope ratios suggest Permian seawater or Permian evaporites as the main sulfur source. Fluid inclusion composition confirms a contribution of the Permian seawater to the mineralizing fluids and accord with a Permian mineralization age. Organic geochemistry data reflect mixing of hydrocarbons at the ore site and support the hydrothermal-metasomatic origin of the Ljubija iron deposits.
24 citations
TL;DR: In this paper, a combination of X-ray diffraction data and Fourier-Transform Infrared Spectroscopy was used to identify the phyllosilicate and hydrated sulphate minerals on the surface of Mars.
Abstract: Phyllosilicate minerals and hydrated sulphate minerals have been positively identified on the surface of Mars. Studies conducted on Earth indicate that micro-organisms influence various geochemical and mineralogical transitions for the sulphate and phyllosilicate minerals. These minerals in turn provide key nutrients to micro-organisms and influence microbial ecology. Therefore, the presence of these minerals in astrobiology studies of Earth–Mars analogue environments could help scientists better understand the types and potential abundance of micro-organisms and/or biosignatures that may be encountered on Mars. Bulk X-ray diffraction of samples collected during the EuroGeoMars 2009 campaign from the Mancos Shale, the Morrison and the Dakota formations near the Mars Desert Research Station in Utah show variable but common sedimentary mineralogy with all samples containing quantities of hydrated sulphate minerals and/or phyllosilicates. Analysis of the clay fractions indicate that the phyllosilicates are interstratified illite–smectites with all samples showing marked changes in the diffraction pattern after ethylene glycol treatment and the characteristic appearance of a solvated peak at ∼17 A. The smectite phases were identified as montmorillonite and nontronite using a combination of the X-ray diffraction data and Fourier–Transform Infrared Spectroscopy. The most common sulphate mineral in the samples is hydrated calcium sulphate (gypsum), although one sample contained detectable amounts of strontium sulphate (celestine). Carbonates detected in the samples are variable in composition and include pure calcium carbonate (calcite), magnesium-bearing calcium carbonate (dolomite), magnesium, iron and manganese-bearing calcium carbonate (ankerite) and iron carbonate (siderite). The results of these analyses when combined with organic extractions and biological analysis should help astrobiologists and planetary geologists better understand the potential relationships between mineralogy and microbiology for planetary missions.
23 citations